1. Field of the Invention
The invention relates in general to a burner for combusting gaseous fuels.
2. State of the Art
It is known to produce charcoal by pyrolyzing wood chips under a reducing atmosphere (oxygen deficient) in a multiple hearth furnace. This pyrolysis produces gases which are not completely combusted. To recapture the heat content of these pyrolysis gases, the gases have been passed to an afterburner to complete combustion of the gases and from the afterburner passed to a heat exchanger.
Heretofore, this approach to recapturing the heat content of pyrolysis gases has not been entirely satisfactory. Afterburners have commonly allowed uncombusted gases to pass through to the heat exchanger. Such uncombusted gases cause damage to the heat exchanger by providing a reducing atmosphere which is conducive to corrosion in the heat exchanger and by allowing combustion, which results in overheating, to occur in the heat exchanger.
In addition, these afterburners have typically employed small diameter orifices and passages to convey the pyrolysis gases to achieve good mixing of the pyrolysis gases with oxygen which is needed to combust the gases. These small orifices and passages are undesirable because of possible clogging by particulates carried in the gases.